Field of the Invention
The present invention relates to a power supply apparatus, and especially relates to a power supply apparatus with an extending hold up time function.
Description of the Related Art
The power supply apparatus is a very common electronic apparatus. The power supply apparatus is used to supply power to the load apparatus to drive the load apparatus. Therefore, the power supply apparatus is very important. Usually, the power supply apparatus is connected to the alternating current power supply apparatus to receive the alternating current power.
The design of the hold up time of the related art power supply apparatus is based on the capacitor energy-storage formula: (½)C(V22−V12)=PT, wherein the C means the bulk capacitor, the V2 means the operating voltage, the V1 means the cut-off voltage, the P means the output power of the power supply apparatus, and the T means the hold up time. According to the formula mentioned above, in order to extend the hold up time, the designer usually increases the bulk capacitor. However, the design of the modern power supply apparatus is slimmer and lighter today. The bulk capacitor has a larger volume, so that increasing the bulk capacitor is not practical. This problem needs to be resolved.